Table Of Contents
Table Of Contents

Measuring Channel Utilization

Goals

In this example we explore the channel utilization statistics of wired and wireless transmission mediums.

INET version: 4.4

The Model

The channel utilization statistic is measured by observing the packets which are transmitted through the transmission medium over time. For both wired and wireless channels, the utilization is measured for any pair of communicating network interfaces, separately for both directions. This statistic expresses the relative usage of the channel with a value between 0 and 1, where 0 means the channel is not used at all and 1 means the channel is fully utilized.

Channel utilization is a statistic of transmitter modules, such as the PacketTransmitter in LayeredEthernetPhy. The channel utilization is related to channel throughput in the sense that utilization is the ratio of throughput to channel datarate. By default, channel utilization is calculated for the past 0.1s or the last 100 packets, whichever comes first.

These values are configurable from the ini file with the interval ([s]) and numValueLimit parameters, as module.statistic.parameter. For example:

*.host.eth[0].phyLayer.transmitter.utilization.interval = 0.2s

Here is the network:

../../../../_images/Network10.png

The hosts are connected by 100 Mbps Ethernet.

We configure the hosts to use the layered Ethernet model, and the source host to generate UDP packets with around 48 Mbps. Here is the configuration:

[General]
network = ChannelUtilizationMeasurementShowcase
sim-time-limit = 1s

# source application with roughly ~48Mbps throughput
*.source.numApps = 1
*.source.app[0].typename = "UdpSourceApp"
*.source.app[0].source.packetLength = 1200B
*.source.app[0].source.productionInterval = exponential(200us)
*.source.app[0].io.destAddress = "destination"
*.source.app[0].io.destPort = 1000

# destination application
*.destination.numApps = 1
*.destination.app[0].typename = "UdpSinkApp"
*.destination.app[0].io.localPort = 1000

# enable modular Ethernet model
*.*.ethernet.typename = "EthernetLayer"
*.*.eth[*].typename = "LayeredEthernetInterface"

# data rate of all network interfaces
*.*.eth[*].bitrate = 100Mbps

Results

We measure the channel utilization in the source host (the source.eth[0].phy.transmitter.utilization statistic). Here are the results:

../../../../_images/ChannelUtilizationHistogram.png
../../../../_images/ChannelUtilizationVector.png

Note

This is the channel utilization in the source -> destination direction. Utilization in the other direction on this link could be measured with the utilization statistic in destination, but in this case there is no traffic in that direction.

Sources: omnetpp.ini, ChannelUtilizationMeasurementShowcase.ned

Discussion

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